Process for dyeing manufactured articles of polyamidic resins

ABSTRACT

A PROCESS IS DISCLOSED FOR OBTAINING COLORINGS WITH DISCONTINUOUS OR SHADED COLOR EFFECTS OF THE FAKE-TORTOISE TYPE OR OF THE MARBLE TYPE ON FORMED ARTICLES OF POLYAMIDIC RESINS, SUCH AS SPECTACLE FRAMES, HAIR CLIPS, BAG HANDLES, COMBS, ETC., WHEREIN TO A SLIGHTLY ACIDULATED AQUEOUS DYEING BATH CONTAINING AT LEAST ONE DISPERSED DYE, A SMALL QUANTITY OF OIL SUFFICIENT TO COVER AT MOST 3/4 OF THE FREE SURFACE OF THE DYEING BATH IS ADDED, THE OBJECT OF POLYAMIDIC RESIN BEING THEN DIPPED INTO SAID DYEING BATH. THE DYEING BATH, BEFORE THE OBJECT IS DIPPED INTO IT, MAY BE SLOWLY STIRRED SO THAT THE OIL WILL BE SPREAD OVER THE SURFACE OF THE BATH IN IRREGULAR SPOTS OR PATTERNS. THE OBJECT MAY BE SLOWLY TURNED ABOUT ITSELF IN SUCH A WAY THAT IT WILL ACCOMPLISH A COMPLETE ROTATION AT LEAST ONCE EVERY 2-3 MINUTES.

United States Patent Oihce ,956 Int. Cl. D0611 1/18, 1/20, 3/24 US. Cl. 8-4 6 Claims ABSTRACT OF THE DISCLOSURE A process is disclosed for obtaining colorings with discontinuous or shaded color effects of the fake-tortoise type or of the marbled type on formed articles of polyamidic resins, such as spectacle frames, hair clips, bag handles, combs, etc., wherein to a slightly acidulated aqueous dyeing bath containing at least one dispersed dye, a small quantity of oil sufficient to cover at most of the free surface of the dyeing bath is added, the object of polyamidic resin being then dipped into said dyeing bath. The dyeing bath, before the object is dipped into it; may be slowly stirred so that the oil will be spread over the sur-.

face of the bath in irregular spots or patterns. The object may be slowly turned about itself in such a way that it will accomplish a complete rotation at least once every 2-3 minutes.

The present invention relates to a process for dyeing objects made of polyamidic resins such as spectacle frames, hair clips, bag handles, combs, etc., with discontinuous or shaded color effects such as for instance marbled effects or imitation of natural tortoise.

Processes are already known for obtaining objects made of polyamidic resins colored with color spots of different color intensity with marbled or natural tortoise effects.

According to one of those conventional processes, the coloring was obtained .by bulk pigmentation of the molten product. This bulk coloring, however, had the drawback of worsening the intrinsic mechanical characteristics of the manufactured article, and in particular it reduced its impact resistance.

According to another known process, the dyeing was carried out by covering the object to be dyed with a suitable template or stencil so as to leave uncovered a few surface zones which were then dyed by a suitable method, for instance by spraying, smearing or the like. Such a process, however, required a considerable waste of time and dye and furthermore it was not possible to obtain thereby colorings of various shades.

Thus, the object of this invention is to provide a process that will allow the elimination of all of the drawbacks of the previous processes and to enable one to obtain excellent imitations of particularly valuable products.

It has now, surprisingly, been found in accordance with this invention that colorings with discontinuous and shaded color elfects, such as artificial tortoise-shell or marbled effects on objects formed from polyamidic resins, are readily obtained by admixing with an aqueous dyeing bath, slightly acidulated and containing at least one dispersed dye, a small quantity of oil sufficient to cover at most of the free surface of the bath and by then dipping the formed object of polyamidic resin into said dyeing bath.

By operating in this way, the intrinsic mechanical characteristics of the polyamidic object are not modified and the coloring thus obtained displays a good resistance against atmospheric agents.

The dyeing technique according to the process according to this invention is relatively simple and inexpensive. It consists in preparing an aqueous dyeing bath slightly 3,677,689 Patented July 18, 1972 acidulated by acetic acid (for instance one having a pH of about 4) containing from 2 to 20% by weight of at least one dispersed dye; in then pouring onto the surface of the bath a small quantity of an oil such that, when spread over the surface, it will cover at most A of the free surface of said bath; in then heating said bath at a temperature between 50 and C.; in slowly stirring the bath so that the oil film will arrange itself on the surface according to irregular spots or patterns; in then dipping the polyamidic resin object to be dyed into said bath and intermittently turning it around itself, for instance, every 2 to 3 minutes; in leaving the object immersed, depending on the intensity of color that one wishes to attain, for a duration of, for instance, from 8 to 20 minutes; in taking out the dyed object from the bath and washing it generously with water; and then finally drying it.

In order to eliminate possible traces of oil from the object, it may be desired to carry out the washing with water to which has been added a small quantity of a nonionic surfactant.

As dispersed dyes one may use dyes belonging to the class of azoic and anthraquinone compound-s, for instance the dispersed dyes commercially available from Ciba, such as the Cibacet Blue F3R (Color lindex: 61505); Cibacet Red 2G (C.I.: 11210); dispersed Cibacet Black (CI: 37235); microdispersed Cibacet Yellow 260 (C.I.: 11855); etc.

As the oil one may conveniently use an oil insoluble in water such as mineral oils, fat oils (vegetable and animal), and artificial and synthetic oils such as for instance the oils commonly used as plastifiers.

By the process of this invention, one may dye any type of polyamide. Particularly good results are obtained with objects of polycaprolactam (well known under the designation Nylon 6).

The dyeing may be carried out either on the anhydrous object or on the object previously conditioned with 3-8% of water.

The following series of examples are given for illustrative and not limiting purposes.

EXAMPLE 1 '(l) A dyeing bath was prepared which contained 4% by weight of Cibacet Blue F3R, by first dispersing the dye in very little water (1:1) at room temperature, and by then pouring the dispersion into hot Water at 50 to 60 C., acidified with 40% acetic acid (1 cc. of acetic acid per 1 liter of water).

(2) Over this dyeing bath was then poured a little mineral oil, known under the trademark: Mobil DTE, in such quantity as to almost cover up A of the free surface of the bath.

(3) The bath was then heated to from 60 to 70 C. and then slowly stirred so that the oil spread on the surface in irregular spots.

(4) Thereupon a spectacle frame of white polycaprolactam with a molecular weight of 17,000 was immersed in the dyeing bath, where it was left immersed for from 8 to 10 minutes, while slowly rotating it about itself every 2 or 3 minutes.

(5 Thereafter the spectacle frame was taken out of the dyeing bath, washed with water, and finally dried with a cotton rag.

The metal parts of the spectacle frame were not dyed or attacked by the slight acidity (pH 4) of the dyeing bath.

The spectacle frame turned out to be dyed irregularly with shaded effects of various grades of blue with an excellent and very attractive ornamental effect.

3 EXAMPLES 2, 3 AND 4 In these examples the same procedure was repeated as in Example 1, using however instead of Cibacet Blue F3R (C.I.: 61505) the following dyes, respectively:

Cibacet Red 26 (C.I.: 11210), Cibacet Black, dispersed (C.I.: 37.235), Cibacet Yellow 2GC, microdispersed (C.I.: 11855).

The results attained by these dyes Were just as excellent as those of Example 1.

EXAMPLES 5, 6, 7 AND 8 Here Examples 1, 2, 3 and 4 were repeated, but using a dyeing bath containing 2% of the respective dyes and having a temperature of 100 C. The results obtained were just as excellent as those obtained in the case of Example 1.

EXAMPLE 9 In this case the dyeing of a comb of polycaprolactam (known by the trade name of Renyl by Societa Montecatini Edison) having a molecular weight of about 17,000 was carried out. The dyeing was conducted in two distinct stages in order to obtain a tortoise-like coloring.

(1) In the first stage the procedure was as in Example 1, but using a mixture of two difierent dyes, i.e., a dyeing bath containing 3% of Cibacet Red 26 (C.I.: 11210) and 1% of dispersed Cibacet Black (C.I.: 37.235).

(2) In the second stage the dyed comb from the first stage was dipped into an aqueous dyeing bath containing 4% of Cibacet Yellow 2GC (C.I.: 11855), maintained at a temperature between 60 and 70 C., leaving it immersed in the bath for from 4 to 10 minutes.

The comb was finally taken out of the bath, washed with copious amounts of Water, and then dried.

' The comb turned out to be attractively dyed with shaded e'flects in various grades of tortoise color.

What is claimed is:

1. A process for obtaining colorings with discontinuous or shaded color efiects of the fake-tortoise type or of the marbled type on formed articles of polyamidic resins, wherein to a slightly acidulated aqueous dyeing bath containing at least one dispersed dye, a small quantity of oil sutficient to cover at most 4 of the free surface of the dyeing bath is added, and the object of the polyamidic resin is then dipped into said dyeing bath; said dyeing bath, before the object is dipped into it, being slowly stirred so that the oil is spread over the surface in irregular spots, and during the dyeing the object being slowly turned about itself in such a way that it will accomplish a complete rotation at least one every 2-3 minutes, and the dyeing bath being maintained at a temperature between and C.

2. A process according to claim 1, wherein the oil is a mineral oil, a vegetable or animal fatty oil, or an artificial or synthetic oil insoluble in water.

3. A process according to claim 1, whereinthe dyeing bath contains from 2 to 20% by weight of at least one dispersed dye.

4. A process according to claim 1, wherein the dispersed dye is selected from the class consisting of azoic and anthroquinonic compounds.

5. A process according to claim 1, wherein the object to be dyed is left immersed in the dyeing bath for from 8 to 20 minutes.

6. A process according to claim 1, wherein the formed object is made of polycaprolactam.

References Cited UNITED STATES PATENTS 1,761,305 6/1930 McGuire 8-16 1,668,934 5/1928 Bracewell 8-16 1,871,920 8/1932 Senior 8-16 2,558,992 7/1951 Stott 18-475 2,524,811 10/1950 Koberlein 8-4 1,774,781 9/1930 Witten.

2,118,781 5/ 1938 'Sallada 91-68 2,439,745 4/1948 Miller 8-62 GEORGE F. LESMES, Primary Examiner R. E. MARTIN, Assistant Examiner US. Cl. X.R.

8-16, Dig. 21; 117-39 

